Air and space vehicles are often required to operate within earth's atmosphere at extreme speeds with the result that air friction upon the surfaces of such high speed vehicles produces sufficient heat to raise certain portions of the air and space vehicles to temperatures which exceed the operating limits of most, if not all, metal vehicle structures. Exposure to such elevated temperatures subjects the vehicle to potential structural failure often with disastrous results.
To protect critical surfaces and edges of air and space vehicles during such extreme temperature operation, practitioners in the art provide thermally protective cover structures upon such surfaces and edges which comprise heat resistant thermally insulative protective tiles or panels. In most instances, protective tiles are attached to the host air or space vehicle using adhesive attachment or mechanical fasteners and standoff.
Adhesive attachment systems have been used extensively for vehicles such as the NASA space shuttle vehicles and other early developed systems. Adhesive attachment has been plagued by recurring problems of reliability and excessive cost which has prompted practitioners in the art to focus primarily upon mechanical fastener and standoff supporting mechanisms within thermal protection systems.
In the most typical of the newly developing thermally protection systems, metal fastener standoffs are mechanically secured to the thermal protective tiles or panels and to the underlying or space vehicle structure. The objective is to provide a plurality of thermally protective tiles or panels which form a covering layer over the vulnerable air or space vehicle surfaces. In an attempt to maintain a smooth substantially continuous thermal protective outer “skin” for the host craft, the attachment of the fastener to the thermally protective tile or panel is usually recessed relative to the outer surface of the thermally protective tile or panel. The recess is then covered with an adhesively secured covering plug typically formed of the same thermally protective material as the tiles or panels.
While mechanical fasteners and standoffs appear to offer the promise of more cost effective alternative to adhesive attachment of thermally protective tiles and panels, the integrity resulting thermal protection system is to some extent dependent upon the adhesively attached covering plugs. In the event any covering plug becomes dislodged or displaced, the underlying metal fastener is exposed to extreme heat during high temperature operation. Under these conditions, an exposed metal fastener becomes a “thermal short” conducting heat directly to the vulnerable overlying surface of the air or space vehicle to which the fastener or standoff is secured. The extreme heat conducted by the fastener to the supporting structure of the air or space vehicle compromises the structural integrity of the vehicle and exposes the entire vehicle to dangerous structural failure.
The use of adhesively secured covering plugs within the developing fastener and standoff type thermal protection systems is both costly and undesirable in that it continues to raise concerns as to the overall system reliability and safety of such thermal protective systems.
Faced with the critical need to provide safer, more reliable thermal protection systems for air and space vehicles and the concurrent need for simultaneously reducing costs of fabrication and maintenance of such thermal protection systems, practitioners in the art have provided a variety of thermal protection apparatus. For example, U.S. Pat. No. 7,377,469 issued to Cherian provides for absorbing the differences between the dimensions of tiles and the dimensions of a spacecraft's body, while still holding the tile, during temperature changes during the operation of the spacecraft. The tile are attached to the body using Tie Rods (TRs) or Flex Joints or fasteners. The tie rods flex in the expected direction(s) of the deformation. The tie rod can be shaped to flex in one or more of the directions of the expected deformation.
U.S. Pat. No. 6,293,496 issued to Moe sets forth strain compatible attachment arrangements for securing a plurality of metallic thermal protection (TPS) panels to the substructure of a space vehicle, such as a reusable launch vehicle. The metallic TPS panels are attached in an edge abutting relationship to provide a coterminous outer TPS panel surface that is spaced from the substructure portion of the vehicle and which provides the outside mold line surface of the space vehicle. The attachment arrangement provides a separate stand-off means that is attached at one end to the vehicle substructure and at the other end to one corner of a TPS panel. Each TPS panel when viewed in a plan view will have three or four corners and may assume a number of shapes such as triangular, square, trapezoidal, etc. and may be curved. Each corner of each TPS panel is provided with an apertured insert provided with a plurality of circumferentially arranged locking projections.
U.S. Pat. No. 5,575,439 issued to Heinze et al. sets forth a positive-locking fastening for a thermal protection structure consisting of a plurality of highly heat-resistant, stable panels and a fastener system for fastening a thermal protection structure on an airframe of a spaceplane, particularly a spacecraft intended to reenter the atmosphere. The thermal protection structure is composed of a plurality of highly heat-resistant mechanically stable panels, having a hot gas-exposed panel surface and an airframe surface. The panels may be provided with an additional gap seal, if desired. A plurality of fastening points are provided per panel. These fastening points are arranged at spaced locations from one another and establish a position-locking connection between the thermal protection structure and the airframe. The fastening includes a first fastening point (fixed bearing) which permits no movement or permits only a limited rotary movement of the panel around an axis that is at right angles or nearly at right angles to the airframe surface or to a local tangential plane of the airframe surface. A second fastening point is provided which permits a limited linear (diametric) displacement of the panel, in a direction parallel or substantially in parallel to the airframe surface. At least another fastening point is provided which permits a limited displacement of the panel in all directions which are parallel to or substantially parallel to the airframe surface.
U.S. Pat. No. 5,489,074 issued to Arnold et al. sets forth a thermal protection device, in particular for an aircraft or a space vehicle, comprising a plurality of juxtaposed unit modules each comprising a fairing element provided with fixing tabs, thermal insulation integrated in the fairing elements, and rigid connection means for releasably connecting the fixing tabs to a primary structure that is to be protected. The gap between neighboring fairing elements is limited to a value substantially equal to the minimum value necessary for accommodating thermal expansion of the fairing elements, and the rigid connection means for connecting a fixing tab of a module to the primary structure comprise a ball fixed to the fixing tab in adjustable manner and capable of being locked inside a corresponding socket of a retaining part fixed to the primary structure, the ball being locked in its socket by means of a bolt capable of being released by action exerted against a resilient return force, e.g. from a spring. It then suffices to act on the spring to release the bolt and allow the ball to be inserted into its socket or to be extracted therefrom.
German Patent No. DE 34 11 924 sets forth insulation which is vibration-resistant and mechanically resistant even under unfavorable conditions, which may be for heating gas ducts, such as exhaust gas ducts or turbine support casings, tile elements fastened to the inside of the supporting wall. Each tile element has a box-like covering which is closed on all sides and is made of sufficiently heat-resistant sheet metal with a small thickness, and each tile element consists of a covering wall on the hot side, a storage wall on the cold side and end walls in between.
German Patent No. DE 36 26 514 sets forth a fastener for connecting structural parts in the form of panels, consisting of a pin which is provided with an internal thread and passes through the structural parts, a pot-shaped receptacle which can be clamped to the pin via a threaded bolt which is fitted centrally in the interior of said receptacle, and which receptacle is provided with spring means acting against the entry direction of the pin. Also included are first securing means, which are located in the receptacle and prevent the pin being inadvertently released from the clamped position.
European Patent EP 0 440 544 sets forth a high-temperature thermal protection system consisting of a set of juxtaposed tiles made of a refractory material. The tiles are fixed onto a structure and insulators. This system is designed to be easily dismantlable by virtue of fixing devices, such as screws, which are accessible to tools passing through and deforming a flexible joint placed between two adjacent tiles. The invention applies to the protection of spacecraft or high-speed aircraft, and to the protection of high-temperature vessels or furnaces.
Japanese Patent No. JP 03258699 sets forth receiving fitting for installation on a craft body outer plate through a bottom plate which is constituted with plural tightening fit parts in a crimp shape installed at the circumferential part of a circular plate bottom part, an apertured part formed in the central part.
Japanese Patent No. JP 05203095 sets forth a heat protecting system applied to a body barrel unit and wing upper/lower surfaces of a space vehicle heated to a high temperature within the atmosphere, a high temperature heat insulating material and a high performance heat insulating material are arranged in the outside of a vehicle structural body to cover the outside of these materials with a heat resisting shield. These heat insulating materials and heat resisting shield are fixed to the vehicle structural body by connection fixing tools.
Japanese Patent No. JP 05203096 sets forth a heat protecting system having heat insulating materials arranged on the outside of a vehicle structural body. A heat resisting shield is mounted on the vehicle structural body by a connecting fixture. The connecting fixture is fabricated of a structural body side bolt connected to the vehicle structural body, shield side bolt connected to the heat resisting shield and a bellows for connecting the bolts to each other.
Japanese Patent No. JP 05221398 sets forth a heat protecting material for a space shuttle is fabricated by connecting a surface panel to a main structural panel through a post formed in a shell structure. The supporting post may be formed into a shell structure of hollow cylindrical shape or the like.
Japanese Patent No. JP 07010094 sets forth a heatproof panel mounting member consisting of a metal rod having a male screw part at the outer end part, a ceramic pipe to cover the side portion of the metal rod except for the male screw part, and a pair of metal nuts which are provided with truncated conical portions on their outer circumferential surfaces. The heatproof panel together with a heatproof washer are held between the truncated conical portions of a pair of metal nuts.
Japanese Patent No. JP 09072379 sets forth a vibration insulation fastening mechanism having an insert body fastened to an apparatus; an insert base mounted on a honeycomb sandwich plate through a filler and a spherical body. A viscoelastic material is located between the insert body and the insert base. By converting the deformation due to a vibration mode characteristic of the honeycomb sandwich plate into heat energy accumulated as strain energy in the viscoelastic material, the vibration transmitted from the honeycomb sandwich plate to a host apparatus is reduced.
Japanese Patent No. JP 09126274 sets forth an intermediate support member having a combining plate and a pressing and fixing plate. The fixing plate is pivotably supported on the plate a pivot pin. The combining plate of the intermediate support member is mounted on a support member by an intermediate support member fastening screw.
Japanese Patent No. JP 09263300 sets forth a shaft formed out of a short fiber reinforced ceramic complex material having a conical head portion, a shaft portion and a top protrusion. The entire surface of the shaft is coated with silicon carbide or aluminum oxide to prevent it from binding at elevated temperatures. A high temperature body is inserted into a tapered aperture and an aperture are brought into contact with the head portion. Carbon fiber reinforced complex material bodies and a C collar of niobium alloy coated with aluminum diffusion is bedded between the high temperature structure body and the first protrusion.
Japanese Patent No. JP 10226400 sets forth a strut of light weight space shuttle heat protection material having high heat insulation and a balance of strength, rigidity and deformability. A strut of heat protection material is formed of a flat plate-shaped strut having a substantially narrow strut formed of both structural materials. A space between the surface panel of heat resistant material on the outer side surface and a main structural panel divide both the structural materials into a plurality of components. By connection of various plate-shaped elements and high heat insulating materials, a light weight strut constitution can be obtained, which has high heat insulation suited for a required characteristic of the heat protection material while balancing strength, rigidity and deformability.
Japanese Patent No. JP 2000335500 sets forth a heat insulating structure, capable of withstanding the severe vibrational environment in launching of a spacecraft. A heat insulating structure is formed of a base body, a radiator panel arranged outside the base body and having a long hole therethrough. A spacer is arranged between the base body and the radiator panel and a rod-shaped fastening means is erected on the base body near the spacer.
Japanese Patent No. JP 2004114708 sets forth a heat-resistant structure capable of being easily attached from a front side of a structure. The heat-resistant structure comprises an inclination functioning material body and a pin type fastener integrally molded with an inclination functioning material body. The inclination functioning material body comprises a metal portion integrally formed with a pin type fastener by casting or molding. A composition transition portion is superposed on the metal part and includes a ceramic component superposed on the composition transition.
While the foregoing described prior art devices have endeavored to improve the thermal protective apparatus and art and have in some instances found some use in the art, there remains nonetheless a continuing need in the art for ever more improved thermal protection systems which provide reliability, safety and avoid dependence upon adhesive attachment while simultaneously providing improved efficiency and economy during initial installation and fabrication. Additionally, there remains a continuing need in the art for improved thermal protection systems which also facilitate the repair and replacement of thermally protective tiles and panels during maintenance activities.